三溴偶氮胂分光光度法测定镁合金中稀土总量

Determination of total rare earths in magnesium alloy by tribromoarsenazo spectrophotometry

采用三溴偶氮胂分光光度法,以盐酸分解含单一或混合轻稀土镧、铈、镨、钕和中稀土钐、钆的镁基合金,25mL溶液中0.6g/L显色剂用量为3~8mL,盐酸浓度为0.5~1.0mol/L,在640nm波长下测定了镁基合金中的稀土总量。基体镁对测定无干扰。轻、中稀土总量的质量浓度在0.2~0.8μg/mL范围内与吸光度呈线性,相关系数R2在0.999以上,表观摩尔吸光系数εRE为(1.10~1.19)×10~5 L·mol^(-1)·cm^(-1)。按照实验方法测定各类稀土镁合金样品中稀土总量,结果的相对标准偏差(RSD,n=6)不超过1.6%;并与电感耦合等离子体原子发射光谱法(ICP-AES)测定结果相一致。

The magnesium-based alloy containing single or several light rare earths（lanthanum,cerium,praseodymium and neodymium）and middle rare earths（samarium and gadolinium）was decomposed with hydrochloric acid.In 25 mL of sample solution,the dosage of 0.6g/L chromogenic reagent was 3-8mL.The concentration of hydrochloric acid was 0.5-1.0mol/L.The content of total rare earths in magnesium alloy was determined by tribromoarsenazo spectrophotometry under wavelength of 640 nm.The matrix magnesium had no interference with the determination.When the mass concentration of total rare earths（including light rare earths and middle rare earths）was in range of 0.2-0.8μg/mL,it showed linear relationship to absorbance.The correlation coefficients（R2）were higher than 0.999.The apparent molar absorptivity（εRE）was（1.10～1.19）×10^5 L·mol^（-1）·cm^（-1）.The content of total rare earths in various magnesium alloy samples was determined according to the experimental method.The relative standard deviation（RSD,n=6）was no more than 1.6%.The found results were consistent with those obtained by inductively coupled plasma atomic emission spectrometry（ICP-AES）.